Rice Genotype Evaluation in Nepal's Eastern Terai: Nine Spring Rice Lines Against Hardinath-1

Which rice genotype performed best in the eastern Terai?

Of nine spring (Chaite) rice genotypes tested against the released check Hardinath-1 at Gadhi-3, Sunsari district, Nepal, IR-19-A-5000 performed best overall. It gave the highest grain yield (6.38 t ha^-1), matured earliest (117.3 days) and had the lowest spikelet sterility (16.56%). IR-19-A-4494 (6.20 t ha^-1) and IR-18-A-2294 (6.01 t ha^-1) followed, against 5.01 t ha^-1 for Hardinath-1 and a trial mean of 4.63 t ha^-1.

The study, "Evaluation of Rice (Oryza sativa L.) Genotypes for Growth and Yield Attributing Traits in Eastern Terai, Nepal", was published in i TECH MAG Vol 8: 77–83 (DOI 10.26480/itechmag.08.2026.77.83). Laxmi Katuwal is first author; Bishal Neupane is second and corresponding author, with Laxmi Thakur and Maniram Chaudhary as co-authors. The article states that all authors contributed equally to conception, execution, analysis and preparation of the manuscript.

Why evaluate spring rice genotypes in Sunsari?

Rice is Nepal's principal staple, and spring rice is a short-duration crop that makes use of the window before the main monsoon season. The paper notes that photoperiod-insensitive genotypes are generally grown in this season, and that spring rice can benefit from more sunny days, better control of water and lower weed pressure. Citing MoALD statistics for 2022/23, the authors report that Sunsari is the third-highest rice-producing district in Nepal, with a district productivity of 4.11 t ha^-1, and that it is designated a rice zone under the Prime Minister Agriculture Modernization Project (PMAMP). Yet few spring-season genotypes had been evaluated for the area, and farmers continue to rely on locally available material. Varietal trials like this one quantify yield and its components so that locally adapted genotypes can be identified before any recommendation is made.

How the experiment was designed

• Site: Gadhi-3, Sunsari, Koshi Province (82 m above sea level), within the PMAMP Rice Zone, Inarwa.
• Season: spring (Chaite) 2025; field activities from February to July 2025.
• Entries: IR-18-A-2294, IR-13C121, IR-12C170, IR-132084-B-1191-B-3-5, IR-19-A-5000, IR-19-A-3197, NS-278, NS-188, IR-19-A-4494, and the check Hardinath-1. All were obtained through the PMAMP Rice Zone, Sunsari.
• Design: RCBD, ten treatments, three replications (30 plots), 2 m × 2 m plots (4 m² net).
• Crop management: 25-day-old seedlings transplanted at 20 cm × 20 cm; fertiliser at 120:50:40 kg N:P₂O₅:K₂O ha^-1, with nitrogen split between basal and two top-dressings.
• Analysis: ANOVA for RCBD in GenStat v15, means separated by Duncan's multiple range test (DMRT) at 5%.

Seventeen traits were recorded, including plant height from 30 to 90 days after transplanting (DAT), tillers per square metre, days to maturity, panicle length, filled grains per panicle, sterility percentage, effective tillers, thousand-grain weight, grain yield, biological yield and harvest index.

Results: grain yield and yield attributes of ten genotypes

Genotypes differed highly significantly (p < 0.001) for plant height at 75 and 90 DAT, panicle length, filled grains per panicle, sterility, days to maturity, grain yield and harvest index. Thousand-grain weight and biological yield did not differ significantly. The table below is drawn from the article's Tables 1 and 2, ranked by grain yield. Values sharing a letter in a column do not differ significantly by DMRT.

Source: Katuwal et al. (2026), Tables 1 and 2. LSD (0.05) for grain yield was 1.073 t ha^-1; CV 13.5%.

Two points deserve attention. First, the difference between IR-18-A-2294 and the check (0.99 t ha^-1) was smaller than the LSD and therefore not significant. Second, the two earliest genotypes, IR-19-A-5000 and IR-19-A-4494, did not differ significantly in maturity from Hardinath-1 (121.7 days), but matured significantly earlier than all the other entries.

Harvest index, not biomass, drove the yield ranking

The most informative finding for breeders is that biological yield was statistically uniform across genotypes, while harvest index varied strongly. IR-19-A-4494 produced a below-average biomass (13.35 t ha^-1) yet the second-highest grain yield because it converted 46.65% of that biomass into grain. IR-18-A-2294 produced the largest biomass (16.39 t ha^-1) but converted only 38.06%. In this data set, harvest index tracked grain yield most closely.

Several commonly used selection traits did not line up with yield. IR-18-A-2294 was the tallest genotype and had the longest panicles (28.38 cm), but IR-19-A-5000, with the shortest panicles (19.57 cm), gave the highest yield. NS-188 had the highest tiller density at 60 DAT (447.5 m^-2) but only a mid-range yield and the longest duration (137 days). Filled grains per panicle and sterility separated the high- and low-yielding genotypes most clearly.

Why was spikelet sterility so high?

Seven of the ten genotypes exceeded 29% sterility, and NS-278 reached 53.56%. The authors point out that spring-season flowering in Sunsari coincides with rising pre-monsoon temperatures, and high temperature at anthesis is a well-established cause of spikelet sterility in rice. They present heat stress as a plausible contributor, with later-flowering genotypes exposed for longer, while stating clearly that this could not be tested in the present study. Early maturity is therefore valuable for two reasons: it may reduce exposure to heat at flowering, and it lets the crop be harvested before pre-monsoon rains and frees the field sooner for the main-season crop.

What this means for farmers and extension workers

IR-19-A-5000 combined high yield, early maturity and good spikelet fertility, which is the combination spring-rice growers in the eastern Terai need. The authors recommend IR-19-A-5000 for the eastern Terai subject to confirmation in multilocation trials, and recommend IR-19-A-5000, IR-19-A-4494 and IR-18-A-2294 for further multilocation testing and for use as parents in breeding programmes. None of these lines is a released variety on the strength of this trial alone.

What this means for researchers

• Record harvest index and sterility alongside yield; in this trial they explained more than height, panicle length or tiller number.
• Measure temperature at anthesis if spikelet sterility is a concern, so that the heat-stress explanation can be tested directly.
• Extend to multi-season, multilocation trials to estimate genotype × environment interaction, and add variability, correlation and path analyses, which were outside the scope of this study.

Related work on spring rice decisions is summarised in spring rice sowing time and variety choice in Rautahat, and the wider mechanisation context in the review of rice mechanisation in Nepal. Students analysing a similar trial can follow the RCBD, ANOVA and DMRT guide in R.

Limitations

The results come from a single season at a single site with three replications, so genotype × environment interaction could not be estimated and the rankings cannot be assumed to hold across the eastern Terai. Genetic variability parameters, correlation and path coefficients were not computed, so no indirect selection criterion is proposed. Multi-season, multilocation confirmation is required before any genotype is recommended for release.

How to cite this study

Katuwal, L., Neupane, B., Thakur, L. and Chaudhary, M. (2026). Evaluation of Rice (Oryza sativa L.) Genotypes for Growth and Yield Attributing Traits in Eastern Terai, Nepal. i TECH MAG, Vol 8: 77–83. https://doi.org/10.26480/itechmag.08.2026.77.83

Other articles are listed on the publications page, and the research fit page explains where field trials like this connect to remote sensing and crop modelling. Supervisors and collaborators can reach Bishal Neupane through the contact page.